LESSON 58.] THE SALIVARY GLANDS. 203 



mosing very freely, and contribute to give a fine appearance to the 

 section. The distinction, then, in the tissues of the teeth of fishes 

 is, that in vaso-dentine the vascular tubes are parallel, whereas, in 

 osteo-dentine, they anastomose. 



LESSON LYIII. 



THE SALIVAKT GLANDS. 



862. In the human subject, as in all the higher mammalia, there 

 are three pairs of salivary glands ; these are the parotid, submaxil- 

 lary, and sublingual glands. 



868. The parotid gland (in man) is the largest of the three pairs, 

 and, situate immediately in front of the external ear, extends super- 

 ficially for a short distance over the masseter muscle, and behind the 

 ramus of the lower jaw. 



864. The submaxillary gland is situated in the posterior angle 

 of the submaxillary triangle of the neck. 



865. The sublingual is an elongated and flattened gland, situated 

 beneath the mucous membrane of the floor of the mouth, on each 

 side of the frenum (bridle) of the tongue. 



866. In structure they are conglomerate glands, consisting of lobes 

 which are made up of angular lobules, and these of smaller lobules. 



867. The smallest lobule is apparently made up of granules, 

 which are minute coecal pouches, formed by the dilatation of the 

 extreme ramifications of the ducts. 



868. These minute ducts unite to form lobular ducts, and the 

 lobular ducts constitute, by their union, a single excretory duct. 



869. The above description of these glands applies very generally 

 to the animals in which they are found. 



870. It is not a little remarkable that these three pairs of salivary 

 glands are all found in the class of Reptiles, but never in the same 

 individual ; one animal possesses the parotid ; another, the sub- 

 maxillary ; while a third has only the sublingual. 



871. Food received into the mouth is given at once to the grind- 

 ing teeth, for the double purpose of being thoroughly comminuted 

 and insalivated. One pair of the salivary glands (parotid) has its 

 evacuating duct on the inside of the cheek, opposite to the second 

 molar tooth of the upper jaw, and the action of the jaws, in the act 

 of mastication, not only compels the descent of the saliva in copious 

 streams from these, but simultaneously from the other glands. 



